Propeller mechanism and control



Dec. 13, 1949 G. w. HARDY PROPELLER MECHANISM AND CONTROL 5 Sheet-Sheet1 Filed March 28, 1944 NQN wow 2 mi 9 .5. n E:

ON Wm gwuom/bom GORDON W. HA RDV' Dec. 13, 1949 Filed March 28, 1944 G.W. HARDY PROPELLER MECHANISM AND CONTROL 5 Sheets-$heet 2 INVENTOR.Goauou W. HARDY G. W. HARDY PROPELLER MECHANISM AND CONTROL Dec. 13,1949 Filed March 28, 1944 5 Sheets-Sheet 3 INVENTOR G o R D 0N W HA R DY G. W. HARDY PROPELLER MECHANISM AND CONTROL Dec. 13,1949

Filed March 28, 1944 5 Sheets-Sheet 5 GORDON W. HARDY Patented Dec. 131949 UNITED STATES PATENT OFFICE Application March 28, 1944. Serial No.528,412

3 Claims.

This invention relates to a controllable pitch propeller mechanism andto a control system for adjusting the pitch of the blade or blades whilethe craft served by the mechanism is in motion. The objects includeprovision of an improved mechanism and control of that character andparticularly:

1. A new arrangement for enabling blade pitch adjustment through theintermediary of hydraulic fluid without introducing any of the sealingproblems such as are usually encountered as a result of having to supplyfluid to and removing it "from a rotating assembly during flight.

2. A hydraulically operated remotely controllable variable pitch roeller mechanism haying a self-contained hydraulic system requiring nosealing against fluid leakage between relatively rotating surfaces.

3. A variable pitch propeller in which the blades are adjusted throughthe intermediary of hydraulic fluid in a hermetically sealed system allparts of which, including the entire fluid supply, rotate with thepropeller.

4. -A variable pitch hydraulically acting propeller which 4 willoperate, if required, with hydraulic fluids which have no lubricatingvalue and/or which remain liquid at extremely low temperatures.

5. An adjustable pitch propeller mechanism in which the blades areaccurately, hydrostatically locked in the desired adjusted positions atall times.

6. A hydraulically acting variable pitch propeller mechanism havingmeans to enable variation in speed of blade pitch adjustment in onedirection relative to the speed of adjustment in the opposite direction,as in order to enable rapid blade movement toward reverse pitch whilestill maintaining very gradual blade movement toward high pitch.

7. an arrangement for positive and accurate ropeller blade control foreffecting any pitch variation that could be desired and wherein therotated weight is reduced substantially to a minimum and balanced.

8. A hydraulically acting variable pitch propell'er having an improvedmeans for adjustably limiting the kinetic force applicable to effectblade adjustment.

9. An improved hydraulic variable pitch prop'eller mechanism wherein thetendency of the blades to return toward low pitch position is obstructedby an adjustable automatically operating limiting means enabling returnmo've= (Cl. I'm-160.31)

2 ment only after the force causing such tendency reaches apredetermined or set value. p 10. A variable pitch propeller capable ofmultirange blade adjustment; wherein the rotated parts are of lightweight; wherein the center of gravity is relatively close to the outermain be'ar ing support of the driving shaft; and which propeller caneasily be fitted to the difierent types or styles of aircraft enginecrank shafts now in use without requiring material alteration of thepropeller mechanism or crankshait.

11. An improved variable pitch propeller control for aircraft whichcontrol is operable to effect all desired pitch variations at the willof the operator or pilot of the craft and byone hand in substantiallythe usual position on the control column of the craft.

12. An aircraft control column with finger tip control operable toeffect blade pitch variations while in flight.

13. A variable pitch propeller mechanism wherein blade adjustment andthe control "for the adjusting means are operated respectively byindependent hydraulic systems.

16. An improved blade mounting for a variable pitch propeller.

1'7. An improved mounting mechanism for a blade of a variable pitchpropeller whereby the 1 blade is arranged to be turned for initialadjustment with-reference to a pitch adjusting part and finallyprevented from turning.

18. An improved manner of connecting a propeller blade shank to anassociated rotary element adapted to effect pitch adjustment of suchblade. 19. A propeller mechanism having a nut for attaching themechanism to an engine crankshaft and ope'rable to pull the propellerout of mounted position on such crankshaft when desired, as for generalinspection or propeller replacement.

Further objects and features of the invention will become apparent fromthe following description.

For illustrative purposes the mechanism and -apparat'us are shown-asadapted to serve in a pro- 14. An improved fluid pumping and val'vin'g"peller with three blades. The mechanism serves essentially in the samemanner when a different number of blades is used.

In the drawings:

Fig. 1 is a central longitudinal assembly sectional view in a verticalplane through the hub, said plane centrally cutting the mounting of oneof the blades.

Fig. 2 is a transverse sectional view as indicated by the line 2-2 onFig. l, principally showing the blade adjusting servomotor arrangement.

Fig. 3 is a transverse sectional view taken along the line 3-3 on Fig.1, principally showing a manually controlled limit stop mechanism bywhich the angular adjustment of the blades is ordinarily limited topitch variations suitable for normal forward flight and releasable topermit greater angular adjustment in opposite directions as forfeathering and reverse.

Fig. 4 is a detail assembly view of the limit stop mechanism asindicated by the line 4-4 on Fig. 3.

Fig. 5 is a transverse sectional assembly view as indicated by the line55 on Fig, 1 showing the relative positions of pump and valve unitassemblies for causing actuation of the servomotor and for releasing thelimit stop.

Fig. 6 is a transverse sectional view as indicated by the line 6-45 onFig. 1 showing a preferred mounting arrangement for a set of concentriccams which actuate the movable elements of the pump and valve unitassemblies mentioned in connection with Fig. 5.

Fig. 7 is a partially schematic view showing two cooperating hydraulicsystems one being rotatable with the propeller and the "other beinarranged for actuating the first system and not rotatable with thepropeller, said second system including a pressure accumulator andselective master control valve means for initiating operation'of thedifferent parts of the first system from a common point as on thecontrol column of an aircraft.

Fig. 8 is a view similar to Fig. 7 showing a modification in the mannerof operating the accumulatorandalso showing the selective master controlvalve means diagrammatically.

Fig. 9 is a central sectional assembly view showing, more in detail, theselective master control valve arrangement built into a control columnof the type generally referred to as a control stick.

Fig. 10 is a transverse sectional detail view of the valve mechanism asindicated by the line ill-l on Fig. 9.

Referring further to Figs. 1 to 3, the hub 2 is made as a high tensilesteel shell (e. g. forged steel) having aspheroidally formedhollowcentral portion 3 from which tubular integral arms orblade-supporting barrels 4 extend radially, shown as three in number.The barrels are spaced equally about the axis of rotation of the hub,which is to say-the axis of a crankshaft shown in Fig. 1 as projectingfrom an engine or motor of the craft served. Part of such engine isdesignated E. The hub is supported on the crankshaft 5 through theintermediary of a light weight high tensile steel hub carrier 6 securelyfastened to the hub. A central tubular portion of the carrier is wedgedonto and drivingly keyed to a tapered portion of the crankshaft as at akeyway 1, Figs. 1 and 5.

The tubular portion of the hub carrier extends rearwardly as at 8 andforwardly as at 9 from a wall or web portion n of the carrier (see Fig.5) which latter portion is suitably shouldered as at l l for attachmentto the hub as by a series of screws l2 passing through the wall or weband into an inturned peripherally continuous flange l3 of the hub whichis machined to fit the shoulder surfaces ll of the carrier.

Surrounding and in spaced relation to the rearward tubular extension 8of the carrier, the wall or web In of the latter has an annular flangeportion 14 of slightly less length than the extension 8 and concentrictherewith, so that the two portions 8 and I4 and the supporting wall orweb It constitute a generally imperforate annular channel. The channelis bridged by a cover plate I5 and the annular space l6 so enclosed ishermetically sealed in part by the cover plate through the medium of asoft metal gasket 11 (e. g. lead), squeezed tightly between end shouldersurfaces of the portions 8 and Hi and marginal surfaces of the platel5fwhen the plate is attached to the carrier as by appropriate screwsnot shown but which enter the concentric portions 8 and IA. The gasketI! may be substantially coextensive with the cover plate 15 for furtherinsuring, as nearly as possible, that the enclosed space l6 will behermetically sealed. The screws 12 preferably have soft metal gaskets(or other sealing material, not shown) beneath their heads and forcedagainst the carrier wall or web I0. Further sealing for the space It isprovided in connection with pump and valve units 20, 2! and 22 (seeFigs. 5 and '7) through which the bodily rotated, pitch adjustinghydraulic system, which is supplied with hydraulic fluid exclusivelyfrom the hermetically sealed anular sump afforded by the space It, iscaused to be operated in the desired manner as will be explained later.

The expression hermetically sealed as used herein means that no relativerotation occurs between surfaces which cooperate to obstruct passage offluid therealong or therepast. Where no relative motion between suchcooperating surfaces occurs hermetic sealing may be accomplished evenwithout the use of special sealing material, as by press fitting ofmetal parts; and, when sliding relative motion occurs, the use of knownelastic sealing material, for instance synthetic rubber in annular formand appropriate cross section, is fully effective to accomplish hermeticsealing. But where relative rotation between such surfaces occurs,particularly at speeds comparable, for example, to the averagerotational speed of an aircraft propeller, and particularly when drivenby low horsepower high speed engines such .as used on light weightairplanes, hermetic sealing is impossible as a practical matter mainlybecause of frictionally generated heat and the inability of knownsealing materials to withstand it.

Forwardly beyond the tapered portion of the crankshaft said shaft has athreaded portion 23 lying within a counterbore 24 of the hub carrier. Atubular nut 25 having an internally threaded enlargement at 26 aroundthe threaded portion of the shaft extends forwardly beyond the principalportions of the hub assembly where the nut is provided with a cross borev2! for enabling use of a capstan bar to turn the nut and force ashoulder 29 thereof against a complementary shoulder of the carrier 6 towedge the carrier onto the crankshaft.

A housing 30 for a blade adjusting servomotor generally indicated at 3|,Figs. 1 and 2, is secured to the forward face of the hub 2 centrallythereof. as by a series of screws 32 which pass QAQ QQQQ hro h a ci clar flan e 33 o sa d hous ng n o threaded pe in s in a forw rdl d sposd! t ed fl ge 34 or the ha o 4 split oo ter pin po i d as clea l sh n yF g l, n age circumferentially spaced recesses in th housing 30 andsleeve a and holds the nut 25 against turning out of seated position onthe crankshaft.

T e ade o t ope er ha e th r sh nk portions disposed inside the barrels4 concentric therewith and radiating from a point lying in the region ofthe threaded portion 23 of the crankshaft about which the spheroidallyformed u fa o o o he ub ar generated S cured to the inner ends of theblade shanks by means to be described below are identical bevel, bla eadjusti g gears 40 n, e o laoklash mesh with complementary teeth of amaster orpower gear 4| concentric with the crankshaft 5 and journalledon the hub carrier 6. The gear 4| has its principal'raclial support onthe forward err-.- tremity of the tubular portion 9, of the hub carrierand axial thrust support in a forward direc-v tion by reason of abuttingthe servomotor housing as at 42 over a comparatively wide face of saidhousing. Rearwardly the gear 4| abuts a fairly narrow annular surface 43on said exten,- sion 9 of the hub carrier. The master or power gear 4|has a generally tubular hub portion 44, surrounding the forwardlyextending tubular pore tion 25a of the nut 25 but said hub portion 44 ofthe gear 4| does not ride upon the nut for sup: port- I m y be noted athis Point tha the. en ar ed a ar Por on 2 e nut 2. forms, a shoulder at251 which is adapted to engage the rearwardly disposed forward face ofthe power or master gear at the inner margin of saidface so that whenthe cotter pin is removed from the position illustrated the nut 25 maybe operated to os n t propeller assembl p epara o y to re= moving itfrom operating position on the cranks shaft. The master gear 4| isblocked against forward movement out of the position in whichillustrated by the engagement of said gear with the block or housing 30of the servomotor. By .back turning of the nut 25 until the abutment 25bthereof engages the adjacent rearward face of; the master gear 4| andthen further turning the nut in the same direction, the complementaryconical surfaces of the crankshaft and carrier po t 8 an 9 m y ily beepara e notwith standing any conceivable amount of static friction endto e e t s h epara as when considerable corrosion has occurred at thecontacting conical surfaces. 7

Re r to th e nio or s sho n by 1 and 2, s i e niot r com rises pa a leova inders 45 and 46 formed in the block; orhous g; 3|) and if the blockis made of material such as, aluminum, in order to minimize weight, thenthe cylinders preferably are constituted by steel sleeves 41 pressedinto parallel complementary bores of the block. The cylinder sleeves aremaintained in position and closed at. their oppos. site ends as byremovable threaded plugs or caps 48 of identical construction as obviousfrom Fig. 2. The cylinders 45 are intercepted by an axial bore 4.9through the block 3|] and coaxial with the hub 44 of the master or powergear 4|. Said bore 49 is in surrounding spaced concentric rel a-. tionto the hub 44 and the hub has formed there-,- n pinion or ear teeth 0Whioh. mesh with rash teeth 5| of substantially identical double endedpistons 53 and 54 in the cylinders 45 and 46 T peo i e l om ao ness othe. s omoto ass mb the id t e p ton are ut aw y as ind ca d. n

i 2 and the a k te th 5! o the istons are,

rme o the. o a a po io s. The slee s 4. e al o out a a at mu ua l ajaoen side to eoei th hub. 4 and ar or pinio eeth 0 hereoi- T e en ofthe pistons a e pr i h e ti s a ng cup 5.5 p efe a ly t ch d o the p tns as by cen al crews 56. F an e Port ons o t e eal n u a el -ex andi gn o ti ht sea ing: oontao wi the inner wal of es ective slee Thepressure chambers 51, 51' and 58, 58 beween th sea n u s and. l gs o c s4 are ros co ec d i he m ne s m ical y shown in Fig. '7 bysuitable bores59 and 60 in the e moto b c 30 s ha fl i pl e nd discharged as throughconduits 6| and 62, Fig, 7 ill mov t e two pi ns 3 an 54 m a e u r u inpp ite d rections in d i n e mats ter or power gear through the rack andpinion tooth connections. The manner of forming the necessary passagesin the servomotor blodk; is more clearly described in my copendingapplication Serial No. l98, l92, filed August 13, 1943 now Patent No.2,433,990.

T e g n ral y en lo ed space wi hi the p oeller hub and. inc d ng thebor whi h recei e he hu 49 of the ma ter or p wer ar is aled at theouter end of the servomotor casing as by n. la tic. annu ar ealing. assm y of con nion l form shown at 6 n including a yie ding ea ng d ns in.ontinuo pe iphera ac with a circular surface 3 on the hub 44 of the owergear,

Additional and similar sealing means are provided for the differentblade assemblies, as will e d sor h l er.v so a the space i ide the huband said, bore. 49 can be packed with lubrieating oil or grease and thesame prevented from seeping out of said space or being squeezed out bycentrifugal force,

The blades, a shank portion 63 of one of which is shown in Fig. 1, aresupported for free turning movement about the radial axes of therespective arms or barrels 4 on bearing assemblies including rollers 65and axial thrust bearing ball elemer ts 6,6 retained in position i mi-ch the same manner as are the correspondingly positioned bearingelements of my application Serial No. 498,432 mentioned above. Only oneblade mounting is illustrated and will be described, since all mountingsare the same.

The shank of the blade is strongly secured at coarse rib and grooveformations 81, 88 to half shell sections 6,! and 58. which complementeach ther to orm, in efi a plit g n rally. y indrical mounting andclamping sleeve or collar. The sleev sectiQnS 5'! and 68, lie partlywithin a hardened and ground thrust sleeve 69 which forms an innerbearing racesurfaoe for the rollers 65 and One race for the thrustbearing balls 66. The rollers make contact directly with the inner boreof the barrel 4,, being confined against endwise movement by and betweenan annular rib Iii in the. barrel and an annular shoulder ll provided ona thickeneed 'outer end portion 12 of the, thru s ev 69...

Co p ra i g with the t us surfac s th sleeve iia in supporting theballs, 66 and holding the thrust sleeve and other members securedthereby in placev in the barrel with the esired ork ng ea auoe s a bla ee ing.

nut 13 (blade nut) threaded as at 14 into the outerend of the barrel. Itis advisable to provide a seal between the thrust sleeve and the innerwall of the barrel near the outer end or the thrust sleeve. Such seal isafforded by a continuous elastic sealing ring 15 seated in a peripheralgroove in the thickened portion 72 of the thrust sleeve. The racesurfaces for the balls 66 on the thickened portion 12 of the thrustsleeve and on theblade nut 13 may be simply channel grooves as shown inmy said copending application; but, preferably in order to make theballs constitute both radial and end thrust bearing members and in orderto cause the balls 66 to bear outwardly toward the threads of the bladenut 13, thus tending to lock said nut, opposite sides of the ball racechannels are cut away as indicated at 11 and 78. Thus the balls servemore effectively, in effect, to lengthen the radial bearing for theblade afiorded by the rollers 65 but without having to lengthen therollers. The race formations just described also avoid axial stress onthe'outer rim of the thickened portion 12 which rim occurs by reason ofproviding, in said thickened portion, the recess for the sealing ring15. Additional sealing is provided to retain the lubricant for the balls66 (e. g. grease) by reason of an elastic sealing ring 15a seated in aninternal peripheral groove of the blade nut 13 and blocking egress oflubricant between the blade nut and composite sleeve 61, 68.

The blade gear 49 as will be presently demonstrated is so secured to theblade shank assembly including the thrust sleeve 69 that inward movementof the blade toward the center of the hub is resisted by abutment of endshoulder surfaces of the gear with the hub carrier 6 so that the bladenut 13 when turned in its threaded connection suflicient to take up thedesired clearance adjacent the balls 66, cooperates with such endsurfaces of the gear 40 to prevent more than slight axial movement ofthe blade shank portions inwardly in the barrels 4.

When properly positioned the blade nuts 13 are locked by key members 19secured as by screws 89, one key and one screw being shown. One key issufficient for each blade nut. The slots for the keys in each nut 13 andcorresponding barrel are of unequal number for Vernier adjustment. Forexample, there may be eight key slots 8| in the outer end of the barreland nine key slots 82 in the adjacent end portion of the blade nut 13.This enables fifty-seven relatively turned and keyed positions of nutand barrel.

The blade gear 49 is secured to the sleeve sections 61 and 68 againstrelative axial movement by a threaded connection at 84 between an outerend portion of the hub 85 vof said gear and inwardly extending thickenedflange portions 86 of the sleeve sections 61 and 68. The sleeve sections61 and 68 are pressed into the thrust sleeve 69 so that, opposite thecoarse groove and rib effects 81' and 88 of the sleeve, the blade shankor butt is tightly embraced by the sleeve sections although notsufiiciently tightly to prevent r; tation of the blade about the axis ofthe shank for initial pitch setting and balancing purposes. The innerend of the thrust sleeve 69 has an inwardly thickened portion 99 axiallyabutting the inner ends of the sleeve sections 61 and 68 as at 9|. Thesleeve sections have relatively short (castellate) axial extensions 92lying beyond the plane of the abutment face 9|, which extensions 92 areformed by equally spaced radial key slots in said sleeve sections. Twoof the slots are formed as half slots in each of the sleeve sections 6'!and 68 so that said sections are fully symmetrical. ends of thecastellate, extensions as illustrated. The radial slots of the sleevesections '61 and 68 are diametrally opposite each other and are ofsuitable proportions to receive the locking keys of generallyrectangular cross section, one of which keys is illustrated inlongitudinal section at 93, see left part of gear 46, Fig. 1, Two keys93 are used, one bein omitted for illustrative purposes.

The keys 93 enter radial slots 94 in enlarged flange portions of the huband extend into the slots between the'castellate extensions 92, beingsecured to the gear hub as by individual screws 93, one of which isshown. The preferred arrangement of key receiving slots is the formationof ten slots on the composite sleeve 61, 68 and four slots 94 on the hubof the blade gear so that in tightening the threaded connection at 84,causing an axial abutment at 95 between the thickened end 99 of thethrust sleeve and an adjacent shoulder of the blade gear, there will beconsiderably greater than four relatively turned positions between thegear and sleeve into which a pair of keys can be seated (Vernierarrangement) There can always be an absolutely tight jamming at 95between the gear and adjacent end of the thrust sleeve 69 because ifless space is aiforded for the keys 93 than the width of the key slots,narrower keys can be used so long as a pair of key slots on the gear canbe brought into at least partial alignment with a pair of key slots onthe composite sleeve 61, 68. The above arrangement constitutes a fullVernier jamming adjustment between the gear and sleeve section assembly.

Cooperating with the bearings 66 and the blade nuts 13 in holding theblades in the desired positions along axes disposed perpendicular to theaxis of the crankshaft and also assisting the radial thrust bearings 65,the innermost ends of the blade gears are each piloted on the hubcarrier 6 at radially projecting cylindrical stub portions 96 of thecarrier, which stub portions enter axial counterbores of respectivegears provided with suitable radial bearings at 97, for instance Oilitesleeves.

Additionally, to secure each blade gear 46 to the butt portion of therespective blade, studs, one of which is shown at 99, lie partly withinaxial bores 98 of the blade gears which extend outwardly beyond thebearing sleeves 91. Said studs extend through respective end wallportions I96 of the blade gears for threaded connection at H]! with theblade shanks. The studs 99, in addition to serving to fasten the bladegears to the blade butts, are also adapted to support balancing washersas beneath the heads of the studs and the walls I99 of the gears. Two ofsuch washers are indicated at I92 beneath the head of the stud 99illustrated.

The composite sleeve or collar constituted by the shell sections 61 and68 extends beyond the outer end of the barrel 4 for supporting a lockingand balancing ring thereon. As shown the composite sleeve is providedwith tapered threads at I96 with which complementary threads of the ringHi5 cooperate in such manner that as the ring is turned on the threadsin the direction to move it toward the center of the hub, slightly Thethreads 84 continue to the s'e'parated mating edge portions of thesleeve sections 61 and 68 will be forced toward each other to cause saidsections to be forced tightly against the shank of the blade. In orderfinally to fix the position of the locking ring I to cause greaterclamping force than could possibly be exerted by turning the ring I05and causing contraction at the tapered threaded connection, the ring issplit at one side as at I 07. Enlarged paired portions I98 of thelocking ring receive a tangentially extending clamping bolt I09 havingsuitable means to hold or lock it in clamping position. The nut of thebolt I59 may be wired on. The threaded connection at HIE enables thering to be turned as by hand until it cannot be forced any furtherthereby at the threaded connection I06. Since the only force necessaryto effect strong clamping force by the ring 505 against the sleevesections is exerted by the bolt I09, the ring may be turned with itsrelatively heavier (bolt carrying) portion into any desired positionabout the blade shank, thus enabling partial or complete dynamicbalancing of the propeller assembly in event of unbalance thereof whenfully assembled and mounted on a test spindle.

. Referring to Figs. 3 and 4 a latch mechanism "I I 9 is providednormally to prevent the blades from being shifted above and belowmaximum and minimum pitch angles appropriate for forward driving of thecraft served, while enabling angular movement of the blades on theirswivel mountings below minimum normal pitch for reverse (e. g. forbraking) and above maximum normal pitch (e. g. for feathering). In Fig.3 turning of the master or power gear 4| clock wise effects high pitchand counterlockwise low pitch. As illustrated in Figs. 3 and 4, theforward surface III of the master or power gear 4| is arcuately andaxially indented at regions H3 and I I 4 and between those indentationsis a similar, deeper indentation I I5. Normally seated in theindentation H5 is a latch block In slidable in a non-circular guide boreH8 of a latch mechanism guide sleeve I I9. The guide sleeve may bepressed into a bore Him in the servomotor block 30 as a means formounting the latch block. The latch block has a stem !20 projectingslidably through a partition wall I2I of the guide sleeve H9 into acyclinder bore in which a piston part I22 of the stem slides. A springI23 in a vented forward part of the cylinder normally biases the latchblock II'I toward whatever indented face (I I3, H4, or H5) of the masteror power gear 4! the block may be adjacent.

To operate the latch block to master-gearreleasing position, relative toabutment surfaces HM and H52) defining opposite circumferentially spacedlimits of the indentation II5 of the master gear, fluid is suppliedunder pressure from the pump and valve unit 22, Figs. 5 and 7, through atube I24, Figs. 4 and 7, and a passage I25 to the bore which containsthe piston I22 and at the end of the piston which lies adjacent thelatch block III. The wall I2I serves to limit the latch withdrawingmovement to such distance that when the latch block is moved out of theindentation H5 it is in operative alignment 'with the abutment shouldersIlia and HM of the indentations H3 and H4 respectively.

5 .Once the latch block I I1 is withdrawn from the latch block the fluidforce which withdrew the block may then be released with assurance thatthe gear will finally be arrested in full feathering or safe reversepitch position by one or the other of two abutments H3a or II4 arespective to the indentations H3 and H4, deend n on w i ra on is s le td a e d s red ab o mal p h ad u tm t- Referring further to Fig. 7wherein the pitch adjusting servoniotor, pitch limit latching abutmentand pump-valve units Z9, 2! and 22 are sho n dia matically s ou h in a nl plane intersecting the supply sump l6, earlier described, it may benoted that the pump Valve unit 2}}, which is the unit shown in detail inFig. 1, i5 Dperatively related to the conduit 62 leading to the space 58of the servomotor and the unit ZI is operatively related to the conduit6| l ad to the s r orh o pac Th mpvalve unit 22 is operated, as will beexplained later, to supply fluid through the duct I'M to the latchmechanism H0 of Figs. 3 and i earlier deribed The hummv l u i s 20 and2! are n ar y dentical in co struc on d ff ing e en iall only in postion) hen e he s o g f unit 0 on Fi 1 wi suffioe to explain theconstruction of the unit 31,. The pump mechanisms of the units 30 and 2|are positively actuated to supply hydraulic fluid to the servomotor andthe valve mechanisms of the units 20 and 2I are positively actuated forfluid discharge purposes in respect to the servomotor as will later bemore fully ex:- plained.

Each of the pump and valve units 20 and 2| comprises a generallycylindrical body portion I30, provided intermediate of its cylindricalexterior surface and near its forward end with a continuous annularflange I3I seated against an annular sealing gasket I3I of soft metallocated in a counterbore portion of a through bore I32 in the'wall orweb I I} of the hub carrier. At the rearward end of the body I30 thesame is abutted b an d c n I h ch i at d n a e ra l opposed counterboresurfaces I34 in the portions Send I 4 of the carrier. Said counterboresurfac s in e c pt only the ce tral annular portion 8 and the outerconcentric annular portion I4 of the carrier, which two portions copfilate in forming the inner and outerwalls of the sump space I6 asalready described. The end cap I33' h a p o Jo n q fii f med b 3. ribI35 which telescopes the rearward end of the gene lly c indr body on, da d n c s pr sed fo wa d rin a em ly of the c rr er an h mh alve uni o ato cause th b y I39 to ompres th S I3 d n ed tiohhl ann ar he I 6, n aththe margin f the end cap, when the cover plate I5 is applied and securedby the two series of fastening members (not shown) entering the carrierportions 8 and I4 to close the rear of the sump space H5.

The end cap I33 is maintained in sealed rela-: tion to the body I30 by asoft metal gasket I37 which lies across the rear end faceof the body.I30 and is squeezed between the latter and. the front face of the endcap by a central fastening screw I38 connecting the body and end cap.

As will be seen from Fig. 5, the peripheral surfaces of the bodies 1300fthe respective pump-'v of units valve units 20 and 2I are fully spacedfrom adjatransverse slots in the bodies 130, one slot (that of unit 2|)facing inwardly toward the crankshaft and the other (that of unit20)outwardly therefrom.. The discharge passages for fluid in the bodies(leading to sump) are similarly located and are shown as radial bores inthe bodies I30. Discharge passage I42 of unit 20 extends radially in theassociated body I30 toward the crankshaft,

and the discharge passage I43 of unit 2i extends outwardly away from thecrankshaft. The relatively opposite arrangement of inlet and dischargepassages is provided in order to enable axially extending pump and valveplunger members in pump and valve chambers which intercept orcommunicate with the passages to be located in coacting pairs differentdistances from the crankshaft center as follows.

Pump plunger I44 of unit 20 and valve plunger I45 of unit 2I (see Fig.for relative positions) constitute an operative pair of fluid displacingand discharge elements lying equal distances from the crankshaft axisand being actuated by an operating cam I50 of annular form (Figs. 1andc) non-rotative with the propeller but arranged to be moved byrotation thereof to cause operation of the plungers in timed relationwhere- 'by to energize or condition the blade adjusting 'servomotor formovement in one direction. Valve plunger I46 of unit 20 and pump plungerI41 of unit 2I constitute the other cooperating pair of fluiddischargeand displacing elements; and those elements lie equal distances from thecrankshaft axis appropriate for actuation, through rotation of thepropeller, by a difierent but similar annular cam I5I concentric withthe cam I50 to energize or condition the servomotor for pitch adjustingmovement in the opposite direction. Another annular cam I52 is providedto operate a pump plunger I53 (Figs. 5 and 7) of the pump-valve unit 22serving the hydraulically releasable latch mechanism IIO of Figs. 3 and4.

The cams I50, I5I and I52 and/or the displacing and discharge elementsactuating the servomotor andlatch mechanism of the hermetically sealedrotary hydraulic system could be operated or rendered operative otherthan by power furnished through rotation of the propeller; but in thepresent arrangement all the fluid handling mechanisms of said system areso energized or actuated. The control therefor, as hereinafterdescribed, is a manual control. Automatic or semi-automatic controlcould be used instead or ancillary thereto as already known in thevariable pitch propeller art or, for further example, as shown anddescribed in my prior application Serial No. 498,492.

The three cams I50, I5I and I52 may be pivoted on respective parallelpins I54 carried on arcuate brackets I55 all of similar constructionrojecting forwardly from an adapter plate I56 extending across andsuitably secured fixedly to the forward end of the engine crank caseparallel with the cover plate I5 of the sump I6. The space between theadapter plate and sump cover I5 is closed peripherally by an annularshell I51 secured to the adapter plate and slidably telescoping thecover as shownin Figs. 1 and 6.

12 Y Annular rib portions I58 of the three cams I50, I5I and I52 arerendered active to operate the respective pump and/or valve plungers ofthe units 20, 2| and 22 through frictional contact with floating tappetsor push rods I59 in tubular guide portions I60 of the end caps I33 ofthe various pump-valve units 20, 2I, 22. The tappets, when engaged bythe cam ribs I56 in forwardly swung positions of the cams, bear againststems MM. and H611 of the pump plungers I44 and valve plungers I46respectively of the units 20 and 2| and against a similar stem of thepump plunger I62 of the unit 22 (Figs. 5 and '7) The tappets (lowerright on Fig. 1) comprise cup-shaped metal bodies I63 the closed ends ofwhich bear on the plunger stems to be operated. Self-oiling sleeves I64(e. g. Oilite) seated in the cups embrace and support extremely hardmetal cores I65 such as Carboloy." The exposed ends of the cores bear onthe ribs I58 of the cams and, being supplied with lubricant from theOilite sleeves, have been found to be practically completely wearresisting; and to operate-without appreciably wearing the cam ribs I58.The hardenedsurfaces of the ribs are merely polished by operatingengagement with the tappets at relatively high propeller speeds.

In order that the floating push rods or tappets 159 may be guided for aconsiderable portion of their length by the extensions I60 of the endcaps :33 of the pump-valve units, said extensions are oppositely notchedas at I60 (upper tappet on Fig. 1) to receive the ribs I58 when thelatter are thrust forwardly to valve or pump actuating positions.

The cams I50, I5I and I52 are operated, for example, by hydraulicallyactuated plungers I50, I5I and I52, respectively (Figs. '7' and 8) of ahydraulic system separate from that which rotates with the propeller;and the control for causing selective operation of the cams includes aset of readily manipulatable keys I50, I5I", and I52", Figs. 7 to 10,inclusive, mounted on the control column of the craft served by thepropeller mechanism and arranged to operate control valves of saidhydraulic system as will be described later.

The innermost cam ring I5I may be considered as arranged to actuate theblade adjusting servomotor in the direction to increase blade pitch andthe cam I50 to cause decreasing pitch and reverse pitch. There isactually very little, if any, difference in the operating efliciency ofthe relatively larger and relatively smaller annular cams, for while thespeed of relative movement between such smaller cam and the pump orvalve tappet operated thereby is less than in the case of the larger camand hence the former would tend to generate less total friction, thesmaller cam has to operate at a steeper cam angle than does the largerfor effecting a given pump displacement per cycle, thus approximatelybalancing the operating efficiency of the cams.

The annular cams I50, I5I and I 52 are provided with paired springs I61(Fig. 6) of suitable construction mounted on brackets I60 of the adaptedplate I56 and which project beside and/or between the cams with suitableclearance not shown. The springs normally hold the cams against thefront face 01 the adapter plate. The hydraulic plungers Hi0, I5I and 152act to swing the respective cams forwardly about their pivots I54 intopump and valve actuating positions through the intermediary of slide barcam members I10, HI and I12 supported in guideways in a housing I13. Therespectivecam surfaces of the cain'bars are designated II', Ill and H2and their manner of operation on the annular cams will be obvious fromFigs. 1 and 6. Rearwardly projecting head portions I'I4 of the cam barsare engaged directly by the plungers I50, I5I and I52, which plungerslift the cam bars against the force of return springs I15 in the housingI13. Only one cam bar head, hydraulic plunger and return spring assemblyis illustrated in detail.

Hydraulic fluid is introduced to the three cylinders of plungers I50etc. through conventional tube fittings I16 installed as indicated onFig. 1 on an upper rearwardly extended portion I11 of the adapter plateI56 in overhanging relation'to the engine housing. Balls I18 beneath theplungers I50, I 5| and I52 and located at the effective bottoms of thecylinders for the plungers (see Fig. I) prevent the plungers or sealingcups I19 thereof from closing fluid supply passages I89 leading to thecylinders.

The amount of displacement per cycle (propeller turn) on part of thepumps I44 and I4! can, for example, be varied by adjustment of theforward swinging movement of the cams I553 and I5I wherefore the rate ofoperation of the pitch adjusting servomotor for reverse pitch movementcan be accelerated over forward pitch adjustment movement as may bedesired in order more promptly to obtain reverse pitch for emergencybraking effect on the aircraft served by the propeller mechanism. Sincethe amount of forward swinging movement of the cams, hence the distanceof movement of the pump plungers, is a function of the distance the cambars I and I'll are lifted by the plungers I55 and I5I the cyclic pumpdisplacements may be limited and adjusted by variably positionableabutments as at I8I, Fig. 1, on a cover member I82 of the cam housingI'|3.

Referring further to the construction of the pump-valve units, asexemplified by unit 20 at the lower right in Fig. l, the pump plungerI44 is shown in the position in which it is moved as by a return springI83 to the rear of the inlet slot I49 of the body I30 communicating theplunger cylinder bore I84 of said body with the sump. The plunger I44has an elastic ring seal I85 maintained by elasticity of the sealingmaterial thereof in peripheral hermetic sealing contact with thecylinder bore I84. A discharge passage I85 in the body I39 leads fromsaid cylinder bore I84 to the duct 62 shown as a pipe connected to theforward reduced end of the body I30 as by an appropriate highcompression fitting assembly I87. A spring biased non-return or checkvalve I88 occupies a discharge portion of the passage I86 and is openedonly when the pump plunger is making its delivery stroke.

The valve plunger I46 has, as shown, a poppet type head I90 closingagainst an annular line seat in a valve guiding sleeve |9Icontainingpart of the previously mentioned discharge passage I42 of thevalve. The rearward end of the valve sleeve forms the guidebore for thevalve plunger stem portions, and elastic hermetically acting sealingrings at I92 and I93, around the valve stem and sleeve respectively,block leakage of hydraulic fluid rearwardly from the valve assembly. Adischarge passage I94 in the body I30 carries fluid from the servomotorcylinder space 58 (see Fig. 7) to a counterbore I95 (Fig, l) of thevalve sleeve containing the poppet valve head I90 and a return springI96 bearing thereon in a direction to close the valve when pressure bythe annular cam-I5I on the operating stem is-re= 'movedf The passage I94communicates with the duct 62, I53 (leading from the displacementchamber of the pump I44 to the servomotor) beyond the check valve I88toward the servomotor, so that opening of the valve I46 can alwaysafford free communication of the connected servomotor chamber (58, Fig.7) with the sump I6. The construction of the pump and valve mechanismsof unit 2|, Fig. 7, is essentially thesame as that just described; butagain it should be noted that the positions of pump and valve plungers'of the two units20 and 2| are relatively reversed in respective planesradially of the propeller.

As most clearly brought out on Fig. 5, the inlet I 40 of the pump valveunit 20 is ideally positioned with respect to the outer wall of the sumpI6 from the standpoint of making certain that the inlet will, due tocentrifugal force acting on fluid in the sump, be immersed in hydraulicfluid at all times during rotation of the propeller. During suchrotation if the sump chamber is not completely'full the fluid will tendto draw away from .the inner wall of the sump formed by the rearwardextension 8 of the hub carrier; and, from the standpoint of maintainingimmersion of the pump inlets in hydraulic fluid, the position of thepump valve unit 25 has an advantage over the positionof the unit 2|. Inthe latter case the inlet for the pump, in order for actuation of thepump plunger I41 b the annular cam I5I, must be farther from theperipheral wall of the sump chamber. 1

As a matter of fact, due to the hermetic sealing of the valve and pumpplunger stem portions of units 20, 2| and 22 and the valve sleeve of theunits 26 and 2|, no diminution of fluid in the system has been observedduring operation of the mechanism for long periods of time. In event,however, that the system is not fully charged to begin with or thatleakage should occur, I deem it advisable to provide for diversion offluid to ward the inlet I 4| and that may be accomplished by theprovision of a ramp or deflector of channel shape as at I4Ia, Figs. 1and 5, which deflector 0 is coextensive with the sump axially of thepropeller and which may have its ends substantially in contactrespectively with the outer peripheral wall of the sump chamber and thenear est adjacent face I39 of the body I30 of the unit 2|. Cooperatingwith the deflector in maintaining the inlet I4I charged with fluid atall times, a flow obstructing or damming bafile may be provided as atI4Ib on the far side of the inlet slot I4I with reference to thedeflector I4Ia. The radially inward terminus of the ballle I llb isspaced from the extension 8 of the carrier as clearly indicated on Fig.5 so that fluid can pass beyond the baffle I4Ib and continue tocirculate in the sump.

In order that each discharge valve I45 and I46 will always be opened (i.e. at least cracked) when pumping by the operatively associated pump,I41 and I44, respectively, commences it is necessary for one of the pumpplungers to have a predetermined amount of idle movement before it canstart pumping. Both pump plungers may be arranged for such idlemovement, the same taking place while the forward ends of the plungerstraverse the respective intake passages I40 and Mi (Figs. 5 and 7).

It will be observed by comparison of Figs. 5 and 6 (direction ofrotation of the propeller indicated by an arrow on Fig. 5) thattheannular cam I50 will first openthe' valve I 45 of pumpvaite'unit- 2|"anci'nien begin to move the pump 15 plunger I44 of unit 20, whereastheannular cam II acts in a reversemannerfirst' on the pump I41 and thenon the valve I46.

Whenever thetappet of the pump plungerv I44 approaches the climax of thecam I50 the. ramp of that'cam will already have opened the-co operatingdischarge valve I45; and, since considerably more than half thecircumference .of the cam is operative to hold the valve open,- there isno possibility of the valve being closed :before the climax of the camhas been passed bythe plunger I I 44 and return or rearward movementofsa d p un r b e When the tappet of the pump plunger I41 approachesthe-climax of the cam I5I the coacting valve plunger I46, being inrelatively trailing position, does not open the discharge valve passagefrom the servomotor normally blocked by the controlling valve thereofuntil the pump plunger I4! has been thrust forward a short distance.That distance of plunger movement, however, is insufficient to cut offthe inlet passage I4I, wherefore the pump plunger I41 displaces no fluidtoward the servomotor space 58' (Fig. 7 until the valve plunger I46 hascracked the valve controlling discharge of fluid from the servomotorspace 58.

It is apparent from the above description of operation that the pumpvalve units cannot, with the cam arrangement described, be as much as180 apart taken in a direction opposite the direction of rotation of thepropeller (see Fig. 5) and from pump plunger I41 to valve plunger I46,for otherwise the valve controlled by the latter will not be crackedsoon enough on each cycle. It is also apparent from the abovedescription that, if the conduits GI and $2 communicate the valve andpump chambers of the units 20 and 2I directly with the servomotorcylinder spaces 58' and 58, as diagrammatically shown on Fig. '7, therecan never be any appreciable back pressure opposing the pumping actionof the pump plungers I44 and I47, and that the blades arehydrostatically locked in each adjusted position by the conjoint actionof the plunger operated valves I90 and automatically operating checkvalves I88. Definitely adjustable back pressure may be provided in eachor either direction of operation of the servomotor by the mechanismsgenerally designated I91 and I98, Fig. 1 only, which mechanisms arebuilt into the servomotor block 30 and, in effect interposed in theducts BI and 62, respectively, of Fig. '7. Passages at BI and 62L, Fig.1 (diagrammatically shown), lead from said mechanisms I91 and I98 to theassociated opposed servomotor spaces 58 and 58. If the mechanisms I97and I98 are used they can nearly serve the functions of the dischargecontrol valves I90 in hydrostatically locking the valves against returnmovement after pitch adjustment has been effected.

The mechanisms I91 and I98 serve to prevent return movement of the pitchadjusting servomotor by reactive air thrust on the blades (assuming theassociated discharge valves I90 fail to seat properly) until the airthrust reaches a predetermined value.

Each mechanism I91 and I98 comprises a plunger 200 slidably sealing abore 20I in the servomotor block and maintained normally against thebottom of said bore by a calibrated spring 202 holding the plunger insuch seated position with an initial force, for example, of 400# persquare inch. Each plunger has an axial bore 203 containing a springseated non-return or check valve 204 which admits flow of fluid to theservomotor from the pumps of respective units 20 or 2I comparativelyfreely'but normally blocks return flow. Return flow can only occur whenthe pressure tending to create such flow is built up to a point somewhatgreater than that resisted by the spring 202 (i. e. greater than theassumed 400# per square inch). When that occurs, and the plunger 200 isforced forwardly by said greater pressure, an adjustable check valvereleasepin 205 forces the plug of the check valve off its seat andescapeof fiuid to the forward end OfjhB bore 20 I hence to theinstantaneously. discharging duct 6| or 62 as the case may be. The pin205 is screw threaded for adjustment at 205 into a plug 20'! whichcloses the forward end of the bore 20L Adjustment of the screws 205 canbe effected merely by removing a spinner cap 208 covering the servomotorhousing and suitably attached to the base flange 33' thereof.

The mechanisms 19? and I98 have a special advantage by reason of theirlocation. No piping, subject to possible breakage, is necessary betweensaid mechanisms and the associated servomotor spaces.

The pipe or tubes forming the greater portions of ducts GI and 82 (soindicated) connect with the servomotor block 38 at high compressionelbow and sleeve fitting assemblies 2I0 as shown on Fig. 2; and, tosupport the pipe where they pass through the base of the servomotorblock, diametrally split threaded sleeves 2I I (Fig. 2 only) areutilized. The sleeves contain suitable annular resilient packing (notshown) snugly embracing the respective pipes; but when unscrewed frominserted position the sleeve sections come apart and permit the ferrulenuts on the outer ends of the pipes 0| and 62, constituting fixedenlargements of said pipes, to pass through the threaded openings of theservomotor block 3t. Thus, when said block is removed from the hub forservice or inspection, it is unnecessary to cut the pipes.

Referring further to the pump valve unit 22 which serves the pitch limitstop latch mechanism IIO, said unit is shown only diagrammatically andin Fig. 7. The construction of unit 22, so far as the hermetic sealingmeans thereof is concerned, follows precisely the construction of units20 and 2|, except that the valve of unit 22 does not require any specialsealing means. The intermediate one, I52, of the three annular camscauses actuation of a pump plunger 2 I3 in a pump chamber 2I4 having aninlet slot 2I5 communicating with the sump I8. Fluid forced by theplunger 2I3 passes a non-return or check valve 2I6 and travels throughthe duct (pipe) I24 to the cylinder of the latch releasing piston :22thereof. Only one or two strokes by the pump plunger 2 I 3 is or arenecessary to release the latch block Ill; and, when released, any excessoutput of the pump that may take place is discharged to the sump I0 by aforwardly spring pressed plunger 2I'I in a bore 2I8 of the body of theunit 22, laterally vented at 2I9. The vent 2 i9 is normally covered andnearly closed by the plunger 2H, and excess output on part of the pump213 causes the vent to be uncovered as in a conventional fluidaccumulator. The plunger fits the bore 2I8 loosely enough so that, afterthe latch mechanism I I0 has functioned to release the blade adjustinggearing for abnormal pitch adjustment (feathering or reverse pitch), thepressure in the duct I24 is gradually relieved past said plunger 17211,, through the. clearance space around it, to the vent 2l9.

The manner in which the annular cams are selectively actuated is furtherillustrated by Figs. 7 and 8. The manual control for the actuatinghydraulic system is further shown by Figs. 9 and 10. In Fig. 7 a typicalaircraft control column of the stick type. is shown at 221: having acontrol knob at 22! surmounting a valve body 222 forming part of the topportion of the column. The control column 220, as usual, is hollow andaffords space inside it for fluid conducting (e.g. copper) tubesnecessary for hydraulic control. Operation of respective keys l5E-i52"diverts fluid received from an accumulator chamber 223 and supplied to adistributor manifold in said valve body 222, in a manner selectively tosupply fluid to the actuators I563, l5l', l52 for the an nularcams I50,I51 and E52.

The accumulator of Fig. '7 comprises a cylinder'22 l and piston 225sl'idable therein and urged inv the proper direction to discharge fluid,as through a delivery tube 225, by a spring 22?. The cylinder space atthe spring-contacting end of the piston constitutes a supply sump forfluid returned to the accumulator through a tube 228. The piston has adraw bar or stem 225 leading through a head member 225 of the cylinder22 lbywhich the piston may be drawn back to initial position (right,Fig. 7) after the spring has forced the piston as far as it will go inthe fluid di charging dire'ction. A check valve assembly comprising aflexible disc 230 in sealing relation to an annular series of holes 23|through the piston enables displacement of fluid from the sump end ofthev cylinder toithe discharge end as the piston is moved by the drawbar torestress the expanded spring. A charging inlet. device 232- isprovidedthrough which charging of the. system with fluid may be efiectedor lost fluid replaced.

Torestress, the accumulator spring aflexible tension member orcable 233may be guided by a suitably-supportedv pulley 234- to awindlassdrum 235;fast on: a pin 236- turnably journalled for example on the instrumentpanel 236' of the craft served or some other convenient support on. suchcraft. The end. of the pin 236 whicl1 projects through; the. exposedfaoeof said panel or support. is provided witha crank arm or handle 23?which, when given one turn (e.g. clockwise), so as to bring it against afixed. stop 238 (the position in which shown). fully stresses the springand charges, the. accumulator for. further service of the system. Whenthe operator notes that the handle has returned nearly tov the oppositeside of the: stop 2-38.= he. knows; that. the system. needs rechargingand gives the handle another clockwise turn; A friction. detentmechanism at 265 on the pin 236 prevents: slack in the cable from takingplace as when the handle would tend to remain in. or. fall. toward. adepending position.

The arrangement of. control valves in the body 222. ofthe. controlarrangement according to Fig.

1 is the sameas exhibited by Figs. 8 to 10 wherein.

the valves are shown. in detail.

Referring to Fig. 8. the valve chamber and plunger constructioninsidezthe body 222 is such as to provide a distributor manifold 2 52within said body leading to bores 250, 25l and. 252 within whichvalveplungers 250, 25.1 and 252 are slidably arranged and connected to therespective keys I55. to l52". The, distributor manifold 242 interceptsthe various bores as clearly apparent.

on both Figs- 8 and 9. For illustrative. purposes only, the manifold 242is shownat the right in Fig.

18 8 whereas-said manifold is at the left in the physical embodiment ofthe valve mechanism as shown by Figs. 9' and 10.

The accumulator in Fig. 8 is different in construction from the onedescribed with reference to Fig. 7, but. the accumulator has a pressurespace corresponding to that at 223 on Fig. 7 and so indicated. From saidpressure space, Fig. 8, fluid is discharged to the manifold 2 32 throughthe delivery tube or duct 226. The accumulator spring 221 drives thepiston 223 toward the end of the cylinder 24 .6 to which the deliverytube 226 is attached. The piston 253, in the case of Fig. 8 does notrequire any check valve since fluid is introduced to the space 223 asthrough a tube or duct 225 leading from a hydraulic actuator, indicatedgenerally at 246.

Said actuator may be arranged as a double ended piston 24! in a suitabledouble ended cylinder having duplicate discharge fluid retaining checkvalves at 248. The piston has a supply sump 255 from which fluid isdrawn into the cylinder spaces at the ends of the piston near the endportion of each stroke, as through inlets 249. For reciproeating thepiston a rack and gear mechanism is shown at 257, 255 operable from oneside of the housing as by a handle 259 connected to the gear.

The mechanism 245 can be disposed anywhere in the cockpit or operatorspace of the craft. served and the sump is provided with a fillerextension 269 having a readily removable closure cap 26L Fluid suppliedfrom the accumulator space 223 to; the manifold 2412 is renderedoperative to supply the plunger cylinders of the cam actuating plungersH553. l.5,i-' and I52 selectively simply by manipulationof thedesiredkeys as by the fingers of. one hand disposed adjacent and grasping thevalve body 22 2 forming part of the control column and of suitableproportions so that the pilot or operator can continue to control flightthrough the medium of the column while his hand is inpropeller controlposition.

As shown. onFig. 8 the valve plunger 256 has been. forced tothe right bythe key I50" causing communication of the valve bore 2553 of saidplunger (adjacent manifold 242) with a space 265 Within said bore, andformed by a long neck on the valve plunger, which space 265 is open atall times to communicate with a lateral discharge passage supplying aduct I50 leading to the actuator cylinder of plunger I59. Communicationof the. manifold 242 with the space 255, in the illustrated position ofthe valve plunger 250', is made possible by reason of the provision of ashort neck at 256 on the plunger which, through suitable cross. passagesin the plunger, communicates with a central, bore of the plunger. Thecentral bore communicates-with. the space 265 through other cross.passages aswill be apparent.

The key I52 is maintained in depressed or valve opening position as longas required for thedesired amount of. pitch adjustment. The key I50"preferably controls the propeller for decreased pitch and. when thedesired amount of decrease has been. attained the pilot releases the keyI55 whereupon the duct I52 is then communicated with a return manifold25! formed in; the body and intersecting the three valve plunger boresthereof. Said manifold 25! discharges into a return line correspondingin functionto the tube or duct 228 of Fig. 7 and so markedonFig; 8. Saidduct228 of Fig. 8 empties into the supply sump 255 of the actuatormechanism 246 men id preferably at the supply pipe 260 of saidmechanism. H

The other control valves (plungers 25I and 252) are substantiallyidentical with the one just described and the manifold and passagearrangement thereof serves the valves in the same manner. However, sincethe key I52 and its control valve plunger is for operating the pitchlimit release stop mechanism I I (see Figs. 4 and 7) it is desirablethat some means be provided in order to prevent accidental manipulationof the key I52 or to make manipulation of said key a matter of consciouseffort on part of the pilot or operator.

With that in view an abutment or latch mechanism designated 21b (Figs.'7 and 10) is provided on the body 222 in such position that said latchwould not ordinarily be encountered by any portion of the hand of thepilot or operator. The latch mechanism includes a lever 2'II secured asby a pivot screw 212 inserted into the body 222 at the left side of saidbody as faced by the pilot. A nose portion 273 of the lever 2'II isnormally held in position to block operation of the key I52" by reasonof a spring 214 recessed into the body and bearing outwardly against therearwardly extending arm of the lever 21 I. When the body 222 is grasped(e. g.) by the left hand of the operator or pilot, the palm of that handis poised over the lever 2' but normally in spaced relation to it. Whenat any time, for example, the pilot would have occasion to control thepropeller for reverse pitch, the control column will be close to thebody of the operator so that the palm of said left hand will be stillfarther spaced from the latch operating lever 21 I, such being the usualposition of the control column in landing an airplane. If the pilotordinarily holds the control column in his right hand then it wouldalways require conscious eiiort in order for him to reach around thevalve body 22 the necessary distance in order for him to depress thelatch release lever 2'.

For efiecting an emergency control manipulation for reverse pitch, thepilot first operates the latch 22% to release the key I52, thendepresses said key in order to cause the latch block II! of the latchmechanism H5 on the propeller to be raised out of the indentation II5 ofthe master or power gear M, and, as soon as that has occurred, thendepression of the key I55" will, through the piston element I and thepump and valve mechanism of the hermetically sealed hydraulic system ofthe propeller actuated thereby, cause the servomotor to move towardreverse pitch position as indicated for example on Fig. '7.

For feathering which is also an emergency operatic-n the pilot wouldfirst depress the key I52 and then the key I5I. As a matter of fact thetwo keys in each instance for reverse pitch or feathering can bedepressed simultaneously and the desired respective operations willoccur in proper order.

Referring further to the actual construction of the valve mechanism inthe valve body 222 it may be noted that each of the keys is individuallypressed forwardly as by suitable springs 275 reacting rearwardly againstthe valve body 222 and that the keys are maintained in position againstrotary dislocation or riding on each other by guide dowels 271, theforwardly projecting ends of which are adapted to enter parallelcomplementary semi-cylindrical recesses 218 in the keys. Thefinger-fitting form of the keys is further brought out by Fig. 10. Thekeys may besecured to the stems of the plungers as by cross K cavities232 of the caps 28!! and abut the bottoms of the counterbores in whichthe caps are sup- .ported.

In making the necessary connections of the tubes 225, 228 and I50 etc.to the control valve system, the group comprising tubes I55 etc.,generally indicated at 285 on Fig. '7, are provided with suitable highpressure flexible connections at 285 near the base of the control columnand the metal tubes connected therewith lead into the column and finallyout of an upper portion of it as through grommets 281 (one shown in Fig.9) for connection with the fittings 25 The tubes 226 and 228 aresimilarly provided with high pressure flexible connectors at 288 nearthe base of the column and the upper ends of the metal tubes connectedtherewith communicate with the re spective bores in the body 222constituting the supply and discharge manifolds 242 and 2c? respectivelyas at high pressure fittings 289 and 225, Fig. 9.

Referring further to Fig. '7 it will be observed that in order for theannular cams 25c and 252 (diagrammatically shown) to be in theiroperating positions in which shown, with respect to the pump-valve units20 and 2| (cam I56) and pump valve unit '22 (cam I52), the keys I50" and552" would both be in depressed position. Onl the key I5I controllingcam I5I would be in the released position illustrated.

Iclaim:

1. In a variable pitch propeller, pitch changing mechanism rotatablewith the propeller for varying pitch of a blade thereof in oppositedirections through a normal and abnormal range, a latch mechanism on thepropeller connected with said mechanism and normally blocking operationthereof beyond the normal range, a plurality of actuating membersadjacent but non-rotatable with the propeller for causing respectivelydesired operations of the pitch changing mechanism and for releasing thelatch mechanism, and a series of control devices respective to theactuating members and located remotely of the propeller and side by sidefor operation by a single hand 'of an operator, said control devicesbeing operatively connected respectively to the actuating members.

2. In a variable pitch propeller, a hub, a blade mounted on the hub forpitch adjustment, a reversible hydraulic motor having oppositely actingpressure chambers and a piston means connected with the blade, a duplexpump and valve system on the hub for positively operating the motor inopposite directions and includin units each of which comprises areciprocating pump plunger and a reciprocating plunger type valve, and aplurality of selectively positionable actuating members, each memberoperating to actuate a ump of one unit and a valve of another unitsubstantially simultaneously during successive revolutions of thepropeller to force fluid to one chamber of the motor while venting fluidfrom the other.

3. In a variable pitch propeller, a hub and a blade turnably mountedthereon for pitch adjust- 21 inent in opposite directions, a reversiblehydraulic motor including a piston means connected to the blade andhaving opposed pressure chambers, a source of hydraulic fluid on thehub, two reciprocating pumps connected with said source and respectivechambers, two exhaust valves connected with respective chambers andarranged to return fluid therefrom to said source, the pump of eachchamber being paired with the valve of the other chamber, said pair-seach having Operating parts moved in approximately the same circularpath by and during rotation of the hub, the paths of the two pairs ofoperating parts being diiferent, and non-rotatable actuators forrespective pairs of operating parts, each actuator being selective- 1ymovable from a non-actuating position to an actuating position such thatit engages and disengages its respective pair of operating parts duringrotation of the hub.

GORDON W. HARDY.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date Re. 22,034 Hoover Feb. 24, 19421,372,944 Constantinesio Mar. 29, 1921 1,810,159 Carol June 16, 1931Number Number 22 Name Date Lilley Jan. 10, 1933 Patriarohe May 28, 1935Hoover Dec. 10, 1935 Caldwell Mar. 7, 1939 Austin July 18, 1939 DicksJan. 21, 1941 Smith July 8, 1941 Rindfleisch Sept. 30, 1941 Martin eta]. July 21, 1942 Blanchard et a] Jan. 5, 1943 Blanchard et a1 Jan. 5,1943 Ratie et :al. Mar. 9, 1943 Rindfleisch May 25, 1943 Martin Mar. 7,1944 Lilley Apr. 18, 1944 Hoover Apr. 18, 1944 Unterberg Jul 18, 1944Eves Aug. 1, 1944 Stevenson Dec. 17, 1946 FOREIGN PATENTS Country DateSwitzerland Aug. 17, 1931 Great Britain Feb. 16, 1944 Germany Aug. 30,1934 Germany Feb. 6, 1941 France May 28, 1935 France Mar. 28, 1936France Mar. 24, 1938

